Solvent effects,species and extraction method effects,and coinitiator effects in the grafting of lignin

A general method of grafting lignin has been developed which allows solvent extracted lignin, steam exploded lignin, and kraft lignin to be converted to complex polymers. The lignins grafted have been obtained from aspen, poplar, oak, grasses, and pine. The lignins are research samples, pilot plant products, and commerical products from paper production. Nonionic copolymers of virtually any composition and molecular weight can be made from lignin and 2-propenamide by free radical reaction of 2-propenamide in the presence of the lignin. The water soluble product is a thickening agent and has limiting viscosity number in water at 30°C that vary from 0.1 to 2.0 dL/g. The grafting reaction is rapid and yields of 80 wt % or more can be obtained in as little as 30 min from reactions run in 1,4-dioxacyclohexane or dimethylsulfoxide. The reaction is initiated by a hydroperoxide, chloride ion, and lignin.